Method for producing a crystalline solid from glycine-N, N-diacetic acid derivatives with sufficiently reduced hygroscopicity

ABSTRACT

The present invention relates to a process for preparing a crystalline solid from glycine-N,N-diacetic acid derivatives (e.g., MGDA) of sufficiently low hygroscopicity, which is characterized in that at least one crystalline compound of the formula I is introduced as seed, and a spray granulation is carried out with at least one compound of the formula I, preferably followed by a heat treatment.

This application is a continuation of U.S. application Ser. No.13/391,397 filed Feb. 23, 2012, now U.S. Pat. No. 9,376,649, andincorporated herein by reference, which is a National Stage ofPCT/EP10/05219 filed Aug. 25, 2010 and claims the benefit of DE 10 2009038 951.2 filed Aug. 26, 2009.

Complexing agents for alkaline earth metal ions and heavy metal ions, ofthe kind used in detergents, for example, are typically synthesized inaqueous solution. For certain applications they are required in solidform.

Typical processes for producing solids from solutions are, inparticular, crystallization processes and spray drying processes. It isknown that crystalline solid of the kind produced, for example, inevaporative or cooling crystallization processes may contain water ofcrystallization and under ambient conditions is usually less hygroscopicand more storage-stable than amorphous solid. Through spray dryingprocesses (e.g., in a spraying tower or in a fluidized spraying bed), incontrast, the solid is obtained in amorphous form. In this form thesolid is often highly hygroscopic and when stored in the open underambient conditions it loses its capacity for free flow within a shorttime. In the literature, therefore, measures are described forincreasing the storage-stability of sprayed powders, an example beingthe compacting or aftertreatment of builders for laundry detergents withbenzoic acid in U.S. Pat. No. 3,932,316.

Glycine-N,N-diacetic acid derivatives as complexing agents for alkalineearth metal ions and heavy metal ions in a wide variety of industrialapplication fields are known from WO 94/29421. Theseglycine-N,N-diacetic acid derivatives, an example beingα-alanine-N,N-diacetic acid (MGDA) in the form of the trisodium salt,are highly inhibited in their crystallization, and so typicalcrystallization processes are impossible or uneconomic. Theaftertreatment of amorphous sprayed powders of these compounds withadditives, as for example benzoic acid in accordance with U.S. Pat. No.3,932,316, is undesirable for certain applications, and may also onlyimprove the storage-stability to a limited extent. The stability of acrystalline solid is not attained.

It was an object of the present invention, therefore, to provide avirtually nonhygroscopic, stable, preferably crystalline solidsubstantially comprising glycine-N,N-diacetic acid derivatives which islargely free from additives.

The present invention relates to a process for preparing a preferablycrystalline solid preferably having, for processing and application, forexample, a sufficiently low hygroscopicity and substantially comprisingglycine-N,N-diacetic acid derivatives of the general formula I

in whichR is C₁ to C₃₀ alkyl or C₂ to C₃₀ alkenyl, which may additionally carryas substituents up to 5 hydroxyl groups, formyl groups, C₁ to C₄ alkoxygroups, phenoxy groups or C₁ to C₄ alkoxycarbonyl groups and may beinterrupted by up to 5 nonadjacent oxygen atoms, alkoxylate moieties ofthe formula—(CH₂)_(k)—O-(A¹O)_(m)-(A²O)_(n)—Yin which A¹ and A² independently of one another denote 1,2-alkylenegroups having 2 to 4 C atoms, Y is hydrogen, C₁ to C₁₂ alkyl, phenyl orC₁ to C₄ alkoxycarbonyl, and k is the number 1, 2 or 3, and also m and nare each numbers from 0 to 50, the sum of m+n necessarily being at least4, phenylalkyl groups having 1 to 20 C atoms in the alkyl, a five- orsix-membered, unsaturated or saturated, heterocyclic ring having up tothree heteroatoms from the group consisting of nitrogen, oxygen, andsulfur, which may additionally be benzofused, it being possible for allphenyl rings and heterocyclic rings in the definitions for Radditionally to carry as substituents up to three C₁ to C₄ alkyl groups,hydroxyl groups, carboxyl groups, sulfo groups or C₁ to C₄alkoxycarbonyl groups, or is a radical of the formula

where A denotes a C₁ to C₁₂ alkylene bridge or a chemical bond, andeach M independently of any other is hydrogen, alkali metal, alkalineearth metal, ammonium or substituted ammonium (e.g., organic aminesalts) in the corresponding stoichiometric amounts,which is characterized in that at least one crystalline compound of theformula I is introduced as seed, and a spray granulation (preferably ina granulator) is carried out with at least one compound of the formulaI.

Particularly preferred compounds of the formula I are those as describedin DE 196 49 681.

In an inherently typical way, in a spray granulation, small to ultrasmall droplets in the region of 50 μm of a liquid sprayed throughnozzles are dried in a reaction chamber, by direct heat transfer in awarm or hot air stream to form particles. From aqueous solutions,emulsions or dispersions, for example, ultra small particles (seeds) arefirst produced in the reaction chamber through drying of these sprayeddroplets (alternatively, these seeds may also be introduced at thestart). These seeds are held in a state of suspension (fluidization) ina fluidized bed, and form the surface for layerwise adsorption anddrying of further sprayed droplets. The particles thus produced can beremoved continuously from the drying chamber without interruption to thedrying procedure by means of a classifying discharge in a flexibleway—for example, with freely adjustable particle sizes. On the processof spray granulation, see also H. Uhlemann, L. Mörl,“Wirbelschicht—Sprühgranulation” Springer-Verlag 2000 (ISBN3-540-66985-X).

The process of the present invention is characterized in that at leastone preferably crystalline compound of the formula I is introduced inthe form of seeds and then in an inherently typical way a spraygranulation is carried out with at least one compound of the formula I,preferably in solution (more particularly in aqueous solution, e.g.,about 40% strength).

A spray granulation is carried out preferably with the followingparameters:

Preferred air feed temperature: 90-160° C., preferred air departuretemperature: 40-110° C., preferred product temperature: 40-110° C.,preferred spraying air temperature: 70-110° C., preferred spraying airpressure: 1-6 bar, preferred spraying solution temperature: 50-95° C.

In the process of the invention, for example, liquid raw material (e.g.,a 40% strength aqueous solution of a compound of the formula I) issprayed onto the crystal seeds (of compounds of the formula I) in fluidmotion in the hot air stream, and thereby dries and causes the seeds togrow. This procedure is preferably operated continuously, withpreferably continuous removal of a portion of the product from thegranulator, followed by its treatment with an additional tempering step(heat-treatment step). This lowers the hygroscopicity of the product,preferably by raising the crystalline fraction in the product. Theproduct thus treated represents the end product, and in turn preferablya portion is ground and introduced as new seeds back into thegranulator.

The product is preferably heat-aftertreated (tempered) with thefollowing temperature profile: beginning with a bed temperature of50-90° C., the bed temperature is raised to 90-130° C. over the courseof about an hour, and then held at this temperature for about 60minutes.

The granulator is preferably a fluid-bed spray granulator which isequipped, for example, with a cyclone and/or a filter.

With the process of the present invention, it is necessary preferablyonly right at the beginning to introduce crystalline product, afterwhich a spray granulation (which without introduction of crystallineproduct would only produce far more amorphous granules, for example) andthe subsequent tempering (heat-treatment) results persistently in aproduct having a relatively high crystalline fraction (and,consequently, substantially lower hygroscopicity).

The expression “crystalline” relates preferably to a crystallinefraction of at least 60% by weight.

A solid is said here to be nonhygroscopic or of sufficiently lowhygroscopicity when on storage in the open under normal ambientconditions, e.g., 25° C. and a relative humidity of 76%, it preservesits consistency as (preferably free-flowing) powder or granules over aperiod of at least one day, preferably one week.

The preferably crystalline solid prepared in accordance with theinvention substantially comprises compounds of the formula I, and smallamounts of starting products and/or by-products from the preparation ofthe glycine-N,N-diacetic acid derivatives I may additionally be present.Typical purities for the compounds I, depending on the synthesis processemployed, are 70% to 99.9% by weight, more particularly 80% to 99.5% byweight, based in each case on the solids content.

The crystalline starting substance may be prepared, for example, by theprocess described in DE 196 49 681.

The process of the invention is suitable preferably for those compoundsI in which R is C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl or a radical of theformula

As compound I it is particularly preferred to use α-alanine-N,N-diaceticacid (R=CH₃, MGDA) and its salts. It is preferred, for example, to useits alkali metal salts, ammonium salts, and substituted ammonium salts.

Suitable such salts are in particular the sodium, potassium, andammonium salts, more particularly the trisodium, tripotassium, andtriammonium salt, and also organic triamine salts with a tertiarynitrogen atom.

Suitable bases as a parent to the organic amine salts are, inparticular, tertiary amines, such as trialkylamines having 1 to 4 Catoms in the alkyl, such as trimethylamine and triethylamine, andtrialkanolamines having 2 or 3 C atoms in the alkanol residue,preferably triethanolamine, tri-n-propanolamine or triisopropanolamine.

The calcium salts and magnesium salts are used in particular as alkalineearth metal salts.

Besides methyl, straight-chain or branched alk(en)yl radicalscontemplated for the radical R include in particular C₂ to C₁₇ alkyl andalkenyl, more particularly straight-chain radicals derived fromsaturated or unsaturated fatty acids.

Examples of individual radicals R are as follows: ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, tert-pentyl, neopentyl, n-hexyl, n-heptyl, 3-heptyl (derivedfrom 2-ethylhexanoic acid), n-octyl, isooctyl (derived from isononanoicacid), n-nonyl, n-decyl, n-undecyl, n-dodecyl, isododecyl (derived fromisotridecanoic acid), n-tridecyl, n-tetradecyl, n-pentadecyl,n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl andn-heptadecenyl (derived from oleic acid). For R it is also possible formixtures to occur, more particularly those which derive from naturallyoccurring fatty acids and from synthetically produced technical acids,as a result of oxo-process synthesis, for example.

Serving as C₁ to C₁₂ alkylene bridges A are, in particular,polymethylene moieties of the formula (CH₂)_(k), in which k denotes anumber from 2 to 12, more particularly from 2 to 8, i.e., 1,2-ethylene,1,3-propylene, 1,4-butylene, pentamethylene, hexamethylene,heptamethylene, octamethylene, nonamethylene, decamethylene,undecamethylene and dodecamethylene. Hexamethylene, octamethylene,1,2-ethylene and 1,4-butylene are particularly preferred in thiscontext. In addition, however, branched C₁ to C₁₂ alkylene groups mayalso occur, e.g., —CH₂CH(CH₃)CH₂—, —CH₂C(CH₃)₂CH₂—, —CH₂CH(C₂H₅)—, orCH₂CH(CH₃)—.

The C₁ to C₃₀ alkyl and C₂ to C₃₀ alkenyl groups may carry up to 5, moreparticularly up to 3, additional substituents of the stated type, andmay be interrupted by up to 5, more particularly up to 3, nonadjacentoxygen atoms. Examples of such substituted alk(en)yl groups are —CH₂OH,—CH₂CH₂OH, —CH₂CH₂—O—CH₃, —CH₂CH₂—O—CH₂CH₂—O—CH₃, —CH₂—O—CH₂CH₃,—CH₂—O—CH₂CH₂—OH, —CH₂—CHO, —CH₂—OPh, —CH₂—COOCH₃ or —CH₂CH₂—COOCH₃.

Alkoxylate moieties contemplated include in particular those in which mand n are each independently of one another numbers from 0 to 30,especially from 0 to 15. A¹ and A² preferably denote groups derived frombutylene oxide and especially groups derived from propylene oxide andfrom ethylene oxide. Of particular interest are pure ethoxylates andpure propoxylates, although ethylene oxide-propylene oxide blockstructures may also occur.

As five- or six-membered, unsaturated or saturated, heterocyclic ringshaving up to three heteroatoms from the group consisting of nitrogen,oxygen, and sulfur, which may additionally be benzofused and may besubstituted by the designated radicals, the following are contemplated:tetrahydrofuran, furan, tetrahydrothiophene, thiophene,2,5-dimethylthiophene, pyrrolidine, pyrroline, pyrrole, isoxazole,oxazole, thiazole, pyrazole, imidazoline, imidazole, 1,2,3-triazolidine,1,2,3- and 1,2,4-triazole, 1,2,3-, 1,2,4- and 1,2,5-oxadiazole,tetrahydropyran, dihydropyran, 2H- and 4H-pyran, piperidine, 1,3- and1,4-dioxane, morpholine, pyrazan, pyridine, α-, β- and γ-picoline, α-and γ-piperidone, pyrimidine, pyridazine, pyrazine, 1,2,5-oxathiazine,1,3,5-, 1,2,3- and 1,2,4-triazine, benzofuran, thionaphthene, indoline,indole, isoindoline, benzoxazole, indazole, benzimidazole, chroman,isochroman, 2H- and 4H-chromene, quinoline, isoquinoline,1,2,3,4-tetrahydroisoquinoline, cinnoline, quinazoline, quinoxaline,phthalazine, and benzo-1,2,3-triazine.

N—H moieties in the stated heterocyclic rings ought as far as possibleto be in derivatized form, for instance as an N-alkyl moiety.

In the case of substitution on the phenyl rings or the heterocyclicrings, there are preferably two (identical or different) or, moreparticularly, one individual substituent present.

Examples of optionally substituted phenylalkyl groups and alkyl groupswhich carry heterocyclic rings, for R, are benzyl, 2-phenylethyl,3-phenylpropyl, 4-phenylbutyl, o-, m- or p-hydroxybenzyl, o-, m- orp-carboxybenzyl, o-, m- or p-sulfobenzyl, o-, m- or p-methoxy- or-ethoxycarbonylbenzyl, 2-furylmethyl, N-methylpiperidin-4-ylmethyl or2-, 3- or 4-pyridinylmethyl.

In the case of substitution on phenyl rings and also on heterocyclicrings, the groups in question are preferably groups conferringsolubility in water, such as hydroxyl groups, carboxyl groups or sulfogroups.

The radicals listed above for R should also be understoodcorrespondingly, to be examples of the stated C₁ to C₄, C₁ to C₁₂, andC₁ to C₂₀ alkyl groups.

The crystalline solid prepared in accordance with the invention isespecially suitable as a component for solid detergent formulations. Inaddition, therefore, solid detergent formulations which comprise thecrystalline solid of sufficiently low hygroscopicity, prepared inaccordance with the invention, comprising glycine-N,N-diacetic acidderivatives I, as complexing agent for alkaline earth metal ions andheavy metal ions, in the amounts customary for this purpose, in additionto other customary ingredients of such formulations, are also providedby the present invention. Compositions and customary ingredients ofsolid detergent formulations of this kind are known to the skilledperson and therefore need not be elucidated in any more detail here.

The example below is intended to elucidate the invention in more detail.The glycine-N,N-diacetic acid derivative I used wasα-alanine-N,N-diacetic acid (methylglycine-N,N-diacetic acid, “MGDA”),trisodium salt.

EXAMPLE

The procedure below was carried out in a fluid-bed spray granulatorwhich is equipped with a cyclone, a filter, and a gas scrubber.

The starting material (Trilon® M, liquid, from BASF AG) was heated to90° C. with continuous and intense mixing and was used at thistemperature for the granulation. Under the following conditions, astable granulating operation was achieved:

Process parameters: Feed air temperature 125° C. Departing airtemperature 65° C. Product temperature 65-70° C. Intake air volume 1300m³/h Spraying air temperature 90° C. Spraying air pressure 3 barSpraying solution temperature 80° C.

In order to raise the crystallinity, the product prepared wasaftertreated with a temperature profile commencing with a bedtemperature of 70° C., then raising this temperature to around 110-120°C. over the course of around an hour, and subsequently holding at thistemperature for around 60 minutes.

Screening at 1000 microns and re-use of the ground coarse material ascrystallization seeds for the granulation process led to a stableoperation with a yield of about 20 kg of granules per hour in thedesired quality. The introduction of comminuted material wasadvantageous for the process, in order to maintain the height of thebed, and in order to obtain the product in a crystalline form.

The invention claimed is:
 1. A process for preparing a crystallinesolid, the process comprising spray granulating an aqueous solution of aliquid raw material on a crystalline seed material to obtain thecrystalline solid, wherein the crystalline seed material, the liquid rawmaterial, and the crystalline solid each comprise a glycine-N,N-diaceticacid derivative of formula (I)

wherein R is: a C₁ to C₃₀ alkyl or a C₂ to C₃₀ alkenyl, optionallyhaving up to 5 substituents selected from a hydroxyl group, a formylgroup, a C₁ to C₄ alkoxy group, a phenoxy group and a C₁ to C₄alkoxycarbonyl group and optionally having up to 5 nonadjacent oxygenatoms; an alkoxylate moiety of formula (II)—(CH₂)_(k)—O-(A¹O)_(m)-(A²O)_(n)—Y   (II)  in which A¹ and A² eachindependently are alkylene groups having 2 to 4 C atoms, Y is hydrogen,C₁ to C₁₂ alkyl, phenyl or C₁ to C₄ alkoxycarbonyl, k is 1, 2 or 3, andm and n are each integers of 0 to 50, a sum of m+n being at least 4; aphenylalkyl group having 1 to 20 C atoms in an alkyl part of the group;a five- or six-membered, unsaturated or saturated, heterocyclic ringhaving up to three heteroatoms from the group consisting of nitrogen,oxygen, and sulfur, which may additionally be benzofused, it beingpossible for any phenyl ring and heterocyclic ring of R additionally tohave up to three substituents selected from the group consisting of a C₁to C₄ alkyl group, a hydroxyl group, a carboxyl group, a sulfo group anda C₁ to C₄ alkoxycarbonyl group; or R is a radical of formula (III)

 where A is a C₁ to C₁₂ alkylene bridge or a chemical bond, and each Mindependently is hydrogen, an alkali metal, an alkaline earth metal,ammonium or substituted ammonium in a corresponding stoichiometricamount.
 2. The process according to claim 1, wherein the process isperformed in a granulator and the process further comprises removing apart of the crystalline solid from the granulator, grinding thecrystalline solid to obtain additional crystalline seed material, andintroducing the additional crystalline seed material into thegranulator.
 3. The process according to claim 1, wherein R is C₁ to C₂₀alkyl, C₂ to C₂₀ alkenyl or a radical of formula (III)


4. The process according to claim 1, wherein the glycine-N,N-diaceticacid derivative is α-alanine-N,N-diacetic acid (MGDA) or an alkali metalsalt, an ammonium salt or a substituted amine salt thereof.
 5. Theprocess of claim 1, wherein R is C₁ to C₂₀ alkyl.
 6. The process ofclaim 1, wherein R is C₂ to C₂₀ alkenyl.
 7. The process of claim 1,wherein R is an alkoxylate moiety of formula (II)—(CH₂)_(k)—O-(A¹O)_(m)-(A²O)_(n)—Y   (II).
 8. The process of claim 1,wherein R is a radical of formula (III)


9. The process of claim 1, wherein A is hexamethylene, octamethylene,1,2-ethylene, or 1,4-butylene.
 10. The process of claim 1, wherein thespray granulating comprises an air feed temperature is 90-160° C. 11.The process of claim 1, wherein the spray granulating comprises an airdeparture temperature is 40-110° C.
 12. The process of claim 1, whereinthe crystalline solid temperature obtained by the spray granulating is40-110° C.
 13. The process of claim 1, wherein the spray granulatingcomprises a spraying air temperature is 70-110° C.
 14. The process ofclaim 1, wherein the spray granulating comprises a spraying air pressureis 1-6 bar.
 15. The process of claim 1, wherein the liquid raw materialis at a temperature is 50-95° C.
 16. The process of claim 1, wherein theobtained crystalline solid preserves its consistency as a powder orgranules over a period of at least one day when stored at 25° C. and arelative humidity of 76%.